The present invention disclosed herein relates to a fiber laser device, and more particularly, to a double clad fiber laser device.
Most fiber laser devices having power of less than several watts generate laser light according to a core pumping method in which pump light is incident to a core for pumping. A semiconductor laser is mainly used as the pump light of the fiber laser. The power of the semiconductor laser light incident to the core is limited. Accordingly, the power of the laser light outputted by pumping is also limited. In order to generate laser light having higher power, more pump light has to be incident to fiber. If gain medium fiber having a double clad structure is used, a fiber laser having power characteristics of more than several tens of watts may be implemented.
A double clad fiber (DCF) may include a single mode core, a first clad, and a second clad. Rare-earth elements are added to the core. If pump line is provided to the core, electrons of excited rare-earth elements emit light. The light emitted from the rare-earth elements travels through the core, and oscillates as a laser through a resonator. The first clad of the double clad fiber is formed of silica glass. The second clad of the double clad fiber is formed of glass of low refractive index, in which silica glass contains fluorine, or polymer. Since a difference of the refractive index between the first clad and the second clad is usually greater than about 0.4, light of various incident angles may be accepted from a laser diode. Also, since the diameter of the first clad is relatively greater than the core, the optical receptivity of the first clad is considerably high. The double clad fiber constituted as described above may allow high-power pump light to be incident to the first clad in an array form at one time.
However, technology for enhancing the power of an amplifier or a fiber laser device using the double clad fiber is still required.